Zika Virus Found in Tears

Researchers publish critical findings from Zika mouse model, raising the possibility of new avenues of transmission, as well as confirming the virus' ability to induce cell death in eyes

Research to Prevent Blindness (RPB)-funded researchers at Washington University School of Medicine in St. Louis published a study that shows that genetic material from the Zika virus has been found in tears. The study, fast-tracked for publication in Cell Reports, was conducted in mice, thereby creating an animal model for studying transmission and
treatment of this alarming virus.

Photo credit: Robert Boston at Washington University

The study, published Sept. 6, describes the effect of Zika virus infection on the eyes of mouse fetuses, newborns and adults and raises the possibility that the eye can function as a reservoir for Zika. Adult mouse models confirm that the virus can infect specific regions of the eye, resulting in uveitis and conjunctivitis (a symptom also observed in human patients).

The important question of whether Zika found in the human eye is infectious, through tears or any other medium, needs to be determined through further study. The researchers now are currently planning complementary studies in human patients infected with the virus.

"Even though we didn't find live virus in mouse tears, that doesn't mean that it couldn't be infectious in humans," said Jonathan J. Miner, MD, PhD, an instructor in medicine and paper's lead author. "There could be a window of time when tears are highly infectious, and people are coming in contact with it and able to spread it."

"We are planning studies in people to find out whether infectious virus persists in the cornea, because that would have implications for corneal transplantation," said Rajendra S. Apte, MD, PhD, the Paul A. Cibis Distinguished Professor of Ophthalmology and Visual Science, and one of the study's senior authors.

Even if human tears do not turn out to be infectious, the researchers' detection of live viruses in the eye and viral RNA in tears still has practical benefits. Human tears potentially could be tested for viral RNA or antibodies, a less painful way to diagnose recent Zika infection than drawing blood. The mouse eye could be used to test anti-Zika drugs, and once an effective treatment has been found, dosing in the eye would avoid side effects such as liver toxicity.

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